Conventional gem facets are smooth, flat, polished surfaces. The production of faceted gems typically involves cutting and polishing numerous angular facets about the exterior surface of the gem. They are normally arranged symmetrically about a central gem axis, although certain gems are faceted without regard for geometric symmetry. This produces an optical system of prisms and reflective surfaces that creates multiple visual virtual images of reflected light when viewed.
This invention arose from a discovery that the optical appearance of a faceted gem can be enhanced by producing facets having all or part of their surfaces in the form of curved surfaces that are sections of a cylinder. These unique facets, which shall be termed, "optically magnified facets", can be used in addition to or in place of all or some of the usual planar facets in any gem cutting pattern.
A spherical facet surface cannot be superimposed on a geometric facet pattern having straight facet sides without gaps about the edges of the curved surface. A curved surface that is a section of a cylinder has substantial straight line components that do not appreciably alter conventional gem faceting patterns. Cylindrically curved facets provide optical magnification in a gem without the substantial border areas that would be required if spherical "dimples" were formed about a gem.
The use of optically magnified facets increases the geometric variations available to a gem cutter beyond those possible when producing a gem by use of conventional flat facets. In addition, the optically magnified facets enhance the brilliance and scintillation of the gem. They also have been observed to intensify the color density of the gem in comparison to the natural crystal of a conventionally-faceted gem containing only flat facets. The recognized "fire" observable in diamonds is seen in less-precious gems of a lower refractive index having these uniquely curved facets. They also enhance the color dispersion of light reflected from the gem.
The apparatus and method disclosed herein have resulted in the production of an entirely new form of cut gems having optically magnified facets. The facets can be generated about individual cylinder axes that intersect the gem axis. They can cover all or part of the normal area of a conventional flat facet. The unique axial orientation of each optically magnified facet also permits the cylinder axes to be axially offset from the gem axis in a rotational progression about the gem axis, resulting in a helical pattern of facets not previously obtainable about a cut gem. Scintillation can be further enhanced by the production of reproducible grooved facets across the curved surfaces of the optically magnified facets.